Short and Efficient Synthesis of Coronene Derivatives via Ruthenium-Catalyzed Benzannulation Protocol
SCHEME 1
Hung-Chin Shen, Jhih-Meng Tang, Hsu-Kai Chang, Chia-Wei Yang, and Rai-Shung Liu* Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan, ROC 30043
[email protected] Received June 19, 2005
TpRuPPh3(CH3CN)2PF6 (3 mol %) was very active in catalytic benzannulation of 1-phenyl-2-ethynylbenzenes in dichloroethane (60 °C, 36 h) to afford phenanthrene in 95% yield. This method is applicable to the synthesis of various polycyclic aromatic hydrocarbons via two- and four-fold benzannulations, including various substituted coronene derivatives (53-86% yields) using this catalyst at a moderate loading (10 mol %).
Large polycyclic aromatic compounds such as hexabenzocoronene derivatives1-3 (Scheme 1, eq 1) tend to form columnar liquid crystal mesophases via intermolecular π-π stacking. This structural feature shows promising applications for organic transistors4 and photovoltaic devices.5 The facile and practical synthesis of hexabenzocoronene derivatives,1-3 notably by the work of Mu¨llen and co-workers, enhances the development of these materials for optoelectronic applications.4,5 In contrast with hexabenzocoronenes, published methods for the synthesis of coronenes are plagued with long proce(1) (a) Harvey, R. G. Polycyclic Aromatic Hydrocarbons; WileyVCH: New York, 1997. (b) Sakurai, H.; Daiko, T.; Hirao, T. Science 2003, 301, 1878. (2) (a) Berresheim, A. J.; Mu¨ller, M.; Mu¨llen, K. Chem. Rev. 1999, 99, 1747. (b) Watson, M. D.; Fethtenko¨tter, A.; Mu¨llen, K. Chem. Rev. 2001, 101, 1267. (c) Schmidt-Mende, L.; Fechtenkotter, A.; Mu¨llen, K.; Moons, E.; Friend, R. H.; Mackenzie, J. D. Science 2001, 293, 1119. (d) Hill, J. P.; Jin, W. S.; Kosaka, A.; Fukushima, T.; Ichihara, H.; Shimomura, T.; Ito, K.; Hashizume, T.; Ishii, N.; Aida, T. Science 2004, 304, 1481. (3) (a) Stein, S. E.; Brown, R. L. J. Am. Chem. Soc. 1987, 109, 3721. (b) Mu¨ller, M.; Ku¨bel, C.; Mu¨llen, K. Chem. Eur. J. 1998, 4, 2099. (c) Do¨tz, F.; Brand, J. D.; Ito, S.; Gherghel, L.; Mu¨llen, K. J. Am. Chem. Soc. 2000, 122, 7707. (d) Wu, J.; Watson, M. D.; Tchebotareva, N.; Wang, Z.; Mu¨llen, K. J. Org. Chem. 2004, 69, 8194. (4) (a) Dimitrakopoulos, C. D.; Malenfant, P. R. L. Adv. Mater. 2002, 14, 99. (b) Horowitz, G. Adv. Mater. 1998, 10, 365. (5) (a) Eckert, J.-F.; Nicoud, J.-F.; Nierengarten, J.-F.; Liu, S.-G.; Echegoyen, L.; Armaroli, N.; Barigelletti, F.; Ouali, L.; Krasnikov, V.; Hadziioannou, G. J. Am. Chem. Soc. 2000, 122, 7467. (b) Cravino, A.; Sariciftci, N. S. J. Mater. Chem. 2002, 12, 1931. (c) El-Ghayoury, A.; Schenning, A. P. H. J.; van Hal, P. A.; van Duren, J. K. J.; Janssen, R. A. J.; Meijer, E. W. Angew. Chem., Int. Ed. 2001, 40, 3660. (d) Pourtois, G.; Beljonne, D.; Cornil, J.; Ratner, M. A.; Bre´das, J. L. J. Am. Chem. Soc. 2002, 124, 4436.
dures and inefficiency,6 typically including a pyrolysis step at high temperatures. Only persulfurated coronene derivatives were prepared directly from perchlorocoronene.7 The lack of a convenient and efficient synthesis of coronenes impedes their progress in organic chemistry. Scott and co-workers8 proposed a short synthesis of coronenes from metal-catalyzed cyclization of bis(1,1ethynyl)alkene species, which was prepared conveniently in three steps from commercially available anthraquinone (Scheme 1, eq 2). This approach was, however, inefficient as it gave coronene in only 15-20% yield using 20 mol % RuPPh3(cymene)Cl2 catalyst; no additional coronene example was reported from the use of this catalytic approach. In this study, we sought to accomplish this catalytic transformation using TpRuPPh3(CH3CN)2PF6 catalyst.9 This cationic species readily reacts with terminal alkynes to afford highly electrophilic ruthenium-vinylidenium intermediates and enables the realization of many interesting catalytic cyclizations.9 Catalytic transformations of 3,5-dien-1-ynes, 4-phenyl3-en-1-ynes, and 1-phenyl-2-ethynylbenzenes into benzene derivatives have been studied by either chemical oxidation10 or metal-catalyzed cyclization (Scheme 2).11-13 (6) (a) Jessup, P. J.; Reiss, J. A. Aust. J. Chem. 1977, 30, 843. (b) Craig, J. T.; Halton, B.; Lo, S.-F. Aust. J. Chem. 1975, 28, 913. (c) Van Dijk, J. T. M.; Hartwijk, A.; Bleeker, A. C.; Lugtenburg, J.; Cornelusse, J. J. Org. Chem. 1996, 61, 1136. (d) Rohr, U.; Schlichting, P.; Bo¨hm, A.; Gross, M.; Meerholz, K.; Bra¨uchle, C.; Mu¨llen, K. Angew. Chem., Int. Ed. 1998, 37, 1434. (7) (a) Baird, T.; Gall, J. H.; MacNicol, D. D.; Mallinson, P. R. Michie, C. R. J. Chem. Soc., Chem. Commun. 1988, 1471. (b) Gingras, M.; Pinchart, A.; Dallaire, C.; Mallah, T.; Levillain, E. Chem. Eur. J. 2004, 10, 2895. (8) Donovan, P. M.; Scott, L. T. J. Am. Chem. Soc. 2004, 126, 3108. (9) (a) Madhushaw, R. J.; Lin, M.-Y.; Abu Sohel Md. Shariar.; Liu, R.-S. J. Am. Chem. Soc. 2004, 126, 6895. (b) Odedra, A.; Wu, C.-J.; Pratap, T. B.; Huang, C.-W.; Ran, Y.-F.; Liu, R.-S. J. Am. Chem. Soc. 2005, 127, 3406. (c) Lin, M.-Y.; Maddirala, S. J.; Liu, R.-S. Org. Lett. 2005, 7, 1745. (10) (a) Yamaguchi, S.; Swager, T. M. J. Am. Chem. Soc. 2001, 123, 12087. (b) Mallory, F. B.; Butler, K. E.; Evans, A. C.; Brondyke, E. J.; Mallory, F. B.; Yang, C.; Ellenstein, A. J. Am. Chem. Soc. 1997, 119, 2119. (c) Yao, T.; Campo, M. A.; Larock, R. C. Org. Lett. 2004, 6, 2677. (11) (a) Merlic, C. A.; Pauly, M. E. J. Am. Chem. Soc. 1996, 118, 11319. (b) O’Connor, J. M.; Friese, S. J.; Tichenor, M. J. Am. Chem. Soc. 2002, 124, 3506.
10.1021/jo0512599 CCC: $30.25 © 2005 American Chemical Society
Published on Web 10/21/2005
J. Org. Chem. 2005, 70, 10113-10116
10113
TABLE 2. Ruthenium-Catalyzed Cyclization via a
SCHEME 2
Two-Fold Benzannulationa
TABLE 1. Catalytic Cyclization of 1-Phenyl-2-ethynylbenzene
entry
mol %
solvents
conditionsa
yields (%)
1 2 3 4 5 6 7 8
5.0 5.0 3.0 5.0 5.0 5.0 5.0 5.0
toluene DCE DCE CHCl3 3-pentanone DME CH3CN DMF
100 °C (18 h) 80 °C (10 h) 60 °C (36 h) 80 °C (30 h) 100 °C (12 h) 90 °C (36 h) 90 °C (36 h) 100 °C (36 h)
83 91 95 72 88 13 NR NR
a [1] ) 0.10 M. b The yields of phenanthrene 2 were given after separation from a silica column.
The former process normally requires stoichiometric amount (>1.0 equiv) of suitable oxidants such as I2, ICl, or SbCl5.10 The metal-catalyzed pathway may involve either a metal-π-alkyne or metal-vinylidene intermediate.11-13 Among these catalysts,8,11,12 only RuPPh3(cymene)Cl2 was shown to be active in the 2-fold benzannulation of such functionalities, which can produce more complex polyaromatic hydrocarbons. For our experiments, we selected 1-phenyl-2-ethynylbenzenes to study because it gives a complicated phenanthrene framework. Table 1 shows the efficiency of TpRuPPh3(CH3CN)2PF6 catalyst in the cyclization of compound 1 in various solvents. This ruthenium catalyst (5 mol %) is very active in several solvents (entries 1-5) including toluene (83%), dichloroethane (DCE, 91%), chloroform (72%), and 3-pentanone (88%) but less active or inactive in dimethoxyethane (DME, 13%), acetonitrile (0%), and dimethylformide (DMF, 0%). The same catalytic efficiency is maintained in DCE at 60 °C (36 h) using a 3.0 mol % catalyst (entry 3). The efficiency of this catalyst appears superior to that of other metal catalysts including PtCl2, AuCl3, AuCl, PtCl2(PhCN)2, and In(OTf)3, which requires at least 5 mol % catalyst to attain the same efficiency.12b We extended this new approach to a 2-fold benzannulation to examine its applicability to a short synthesis of polyaromatic hydrocarbons; the results are shown in Table 2. Diyne substrates 3-10 are readily prepared in short steps from commercial sources; their synthetic procedures are provided in Supporting Information. This ruthenium catalyst (10 mol %) works well for the synthesis of dibenzo[a.h]anthracene (11), which was (12) (a) Maeyama, K.; Iwasawa, N. J. Org. Chem. 1999, 64, 1344. (b) Mamane, V.; Hannen, P.; Fu¨rstner, A. Chem. Eur. J. 2004, 10, 4556. (13) (a) Shen, H.-C.; Pal, S.; Lian, J.-J.; Liu, R.-S. J. Am. Chem. Soc. 2003, 125, 15762. (b) Madhushaw, R.-J.; Lo, C.-Y.; Huang, C.-W.; Su, M.-D.; Shen, H.-C.; Pal, S.; Shaikh, I. R.; Liu, R.-S. J. Am. Chem. Soc. 2004, 126, 15560.
10114 J. Org. Chem., Vol. 70, No. 24, 2005
a [3-10] ) 0.05 M, 10 mol % catalyst, DCE, 80 °C, 24 h. b Yields of products were given after separation from a silica column.
obtained in 83% yield (entry 1). We also obtained such an anthracene species (12) fused with two thiophene rings, for which the yield was 74% (entry 2). Tandem cyclization of diyne-ene species (5) with this ruthenium catalyst gave chrysene (13) in 41% yield (entry 3). Synthesis of 9,9′-bianthracene (14) was obtained in 71% yield from binaphthalene (6) bearing two enyne groups (entry 4). This cyclization is applicable to the synthesis of benzo[c]phenanthrene (15) and its oxa- and thiabridged congeners (16 and 17); the yields were 60-81% (entries 5 and 6). Entry 7 shows a successful instance of this cyclization to the synthesis of benzo[ghi]perylene (18) with 75% yield. Among these examples, ribbon type compound 11 has been prepared efficiently (ca. 75%) using photochemical I2-oxidation, which required a sto-
TABLE 3. Synthesis of Coronene under Various
TABLE 4. Ruthenium-Catalyzed Synthesis of Various
Conditions
Coronenes via a Four-Fold Benzannulation
entry
catalyst
conditiona
yields (%)b
1 2 3 4 5 6
TpRuPPh3(CH3CN)2PF6 TpRuPPh3(CH3CN)2PF6 TpRuPPh3(CH3CN)2PF6 TpRuPPh3(CH3CN)2PF6 TpRuPPh3(CH3CN)2PF6 RuPPh3(cymene)Cl2
5 mol %, 1.0 × 10-4 M 5 mol %, 1.0 × 10-3 M 10 mol %, 1.0 × 10-3 M 10 mol %, 1.0 × 10-2 M 20 mol %, 1.0 × 10-2 M 20 mol %, 1.0 × 10-2 M + NH4PF6 (40 mol %)
86 42 67 45 66 15-20c
a DCE, 80 °C, 36 h. b Yields were given after separation from a silica column. c Data were taken from ref 8.
ichiometric amount of oxidant.10b Polyaromatic hydrocarbons 15-17 were previously studied by RuPPh3(cymene)Cl2 (20 mol %) and NH4PF6 (40 mol %), and the respective yields were 60%, 10%, and 95%.8 The acidic nature of NH4PF6 is thought to cause the low yield of product 16. Table 3 shows our efforts to achieve a short synthesis of coronene 20 from bis(1,1-ethynyl)alkene species 19 under various conditions. The cyclization efficiency is highly dependent on the concentration of alkyne 19. A dilute solution is catalytically more efficient (entries 1-5); this condition is expected to weaken the π-π stacking of anthracene 19 to avoid an intermolecular dimerization catalyzed by this ruthenium catalyst.14 A dilute solution (10-2 to 10-3 M) is more suitable for the catalytic transformation because the starting bis(1,1ethynyl)alkene species 19 is sparingly soluble in DCE at 80 °C. A high catalytic efficiency is attained at 10-4 M using 5 mol % catalyst, at 10-3 M with 10 mol %, and at 10-2 M with 20 mol %. We also studied the catalytic activities of various metal catalysts including AuCl3, PtCl2, PtCl2(PhCN)2/2AgBF4, GaCl3, In(OTf)3, and InCl3, which were all inactive at [19] ) 10-3 M with 10 mol % loading. Scott and co-workers8 used RuPPh3(cymene)Cl2 (20 mol %) and NH4PF6 (40 mol %) catalyst to give coronene 20 in 15-20% at [19] ) 10-2 M. This new catalytic reaction provides a short synthesis of various functionalized coronenes via a 4-fold benzannulation of 3,5-dien-1-ynes. We prepared various bis(1,1ethynyl)alkenes 21-26 to examine the generality of this cyclization. These substrates were readily prepared in short steps from commercially available anthraquinone. The catalytic reactions were performed with 10 mol % catalyst at a substrate concentration of 10-3 M; the results are summarized in Table 4. Entries 1 and 2 demonstrate successful synthesis of monosubstituted coronene 27 and 28 bearing a methyl or chloro substituent; the yields were 53-75%. This catalytic reaction is (14) In a separate experiment, we found that phenylacetylene was catalyzed by TpRuPPh3(CH3CN)2PF6 (10 mol %) via a dimerization reaction; the yields of the resulting enyne were 76% and 45% at a phenylacetylene concentration of 0.4 and 0.04 M, respectively.
entry
alkynesa
coronene (yield, %)b
1 2 3 4 5 6
R1 ) Me, R2 ) R3 ) H (21) R1 ) Cl, R2 ) R3 ) H (22) R1, R2 ) (CHdCH)2; R3 ) H (23) R1 ) R3 ) n-C8H17; R2 ) H (24) R1 ) R3 ) OnC4H9; R2 ) H (25) R1 ) R3 ) Ph; R2 ) H (26)
27 (75) 28 (53) 29 (78) 30 (68) 31 (63) 32 (63)
a 10 mol % catalyst, [alkynes] ) 10-3 M, 80 °C, 36 h. b Yields were given after separation from a silica column.
SCHEME 3
compatible with tetracene species 23 (entry 3), which gave its cyclized coronene derivative 29 in 78% yield. This cyclization is successfully extended to the synthesis of disubstituted coronenes 30-32 with 63-68% yields (entries 4-6). The success of TpRuPPh3(CH3CN)2PF6 in the preceding cyclizations relies on its strong preference for the 6-endodig cyclization, and we obtained no byproducts arising from the 5-endo-dig mode. We prepared a deuteriumlabeled sample d2-4 to elucidate the origin of this chemoselectivity (Scheme 3); the resulting product d212 showed a 1,2-deuterium shift during the cyclization. This feature is characteristic of the involvement of ruthenium-vinylidene intermediate.15 NMR signals of polyaromatic species 12 were made on the basis of 1HNOE spectra.16 In summary, we have demonstrated that TpRuPPh3(CH3CN)2PF6 (3 mol %) catalyst was very active in catalytic cyclization of 1-phenyl-2-ethynyl-benzenes in dichloroethane (60 °C, 36 h) and gave phenanthrene efficiently. This catalyst maintains a great efficiency in the two- and four-fold benzannulation of such 4-aryl-3-en-1-yne functionalities and gives good yields of various polyaromatic (15) (a) Trost, B. M. Acc. Chem. Res. 2002, 35, 695. (b) Bruneau, C.; Dixneuf, P. Acc. Chem. Res. 1999, 32, 311. (c) Puerta, M. C.; Valerga, P. Coord. Chem. Rev. 1999, 193-195, 977. (16) The 1H NOE map of compound 12 is provided in Supporting Information.
J. Org. Chem, Vol. 70, No. 24, 2005 10115
SCHEME 4 a
a (a) Trimethylsilylacetylene, PdCl (PPh ) , CuI, HNEt , rt, 8 2 3 2 2 h, 89%. (b) PhB(OH)2, Pd(PPh3)4, Ba(OH)2, THF, 65 °C, 24 h, 73%. (c) TBAF, THF, 0 °C, 2 h, 93%.
hydrocarbons including various substituted coronene derivatives. This method employs a short and convenient synthesis of coronene derivatives. Experimental Section General Sections. Unless otherwise noted, all reactions were carried out under a nitrogen atmosphere in oven-dried glassware using standard syringe, cannula, and septa apparatus. Benzene, diethyl ether, tetrahydrofuran, and hexane were dried with sodium benzophenone and distilled before use. TpRuPPh3(CH3CN)2PF6 catalyst was prepared by heating TpRu(PPh3)2Cl with LiPF6 in CH3CN.9 The diyne substrates 7-10 and tetraynes 19 were prepared according to the procedures described by Scott and co-workers.8 Other tetraynes 21-26 were prepared from the corresponding anthraquinones according to the same protocol. Synthesis of 1,4-Diethynyl-2,5-diphenylbenzene (3). Synthesis of diyne 3 is shown in Scheme 4. To a diethylamine (35 mL) solution of compound S1 (970 mg, 2.00 mmol) were added PdCl2(PPh3)2 (147 mg, 0.209 mmol), copper(I) iodide (74 mg, 0.39 mmol), and trimethylsilylacetylene (470 mg, 4.80 mmol), and the mixture was stirred at 25 °C for 8 h. To this solution was added an aqueous NH4Cl solution, and the mixture was concentrated and extracted with diethyl ether. The ether extract was evaporated and chromatographed through a silica colum (5% ethyl acetate/95% hexane) to give product S2 as a colorless oil (761 mg, 89%). To a THF (10 mL) solution of compound S2 (428 mg, 1.00 mmol) were added Pd(PPh3)4 (170 mg, 0.15 mmol), K2CO3 (1.38
10116 J. Org. Chem., Vol. 70, No. 24, 2005
g, 10.0 mmol), and PhB(OH)2 (360 mg, 3.00 mmol), and the mixture was stirred at 65 °C for 24 h. To this solution was added an aqueous NH4Cl solution, and the mixture was concentrated and extracted with diethyl ether. The ether extract was evaporated and chromatographed through a silica column (hexane) to give S3 (616 mg, 73%) as a colorless oil. To a THF (20 mL) solution of compound S3 (422 mg, 1.00 mmol) was added n-tetrabutylammonium fluoride (1.0 M, THF, 3.0 mL, 3.00 mmol) at 0 °C, and the resulting solution was stirred at 0 °C for 2 h. Column chromatography of the crude product on a silica column with hexane gave diyne 1,4-diethynyl2,5-diphenylbenzene 3 as a colorless oil (258 mg, 93%). Typical Procedure for Catalytic Operation. A long tube containing TpRuPPh3(CH3CN)2PF6 (41.1 mg, 0.05 mmol) was dried in vacuo for 2 h before it was charged with compound 3 (150 mg, 0.54 mmol) and 1,2-dichloroethane (10.8 mL). The mixture was heated at 80 °C for 24 h before cooling to room temperature. The so1ution was concentrated and eluted through a silica column to afford dibenzo[a.h]anthracene 11 (124.5 mg, 0.45 mmol, 83%) as a light yellow solid. Spectral Data for 1,4-Diethynyl-2,5diphenylbenzene (3). IR (Nujol, cm-1): 3296 (m), 3078 (s), 2210 (m), 1613 (s), 1475 (m). 1H NMR (600 MHz, CDCl3): δ 7.62 (m, 6 H), 7.44 (m, 4 H), 7.40 (m, 2 H), 3.11 (s, 2 H). 13C NMR (150 MHz, CDCl3): δ 142.9, 138.9, 134.9, 129.1, 128.1, 127.9, 121.1, 82.5, 81.8. HRMS (EI, m/z) calcd for C12H14 278.1096, found 278.1095. Spectral Data for Dibenzo[a.h]anthracene (11). IR (Nujol cm-1): 3292 (m), 3076 (s), 1614 (s), 1471 (m). 1H NMR (600 MHz, CDCl3): δ 9.13 (s, 2 H), 8.85 (d, J ) 7.8 Hz, 2 H), 7.99 (d, J ) 7.8 Hz, 2 H), 7.89 (d, J ) 7.8 Hz, 2 H), 7.68 (m, 6 H). 13C NMR (150 MHz, CDCl3): δ 132.0, 130.8, 130.2, 129.1, 128.6, 127.5, 127.2, 127.0, 126.8, 122.9, 122.2. HRMS (EI, m/z) calcd for C22H14 278.1096, found 278.1099.
Acknowledgment. The authors wish to thank the National Science Council, Taiwan for supporting this work. Supporting Information Available: Synthetic procedures for other starting alkynes 5 and 6, 1H NMR and 13C NMR spectra, and spectral data of compounds 1-32. This material is available free of charge via the Internet at http://pubs.acs.org. JO0512599
